1. Field of the Invention
This invention deals with the art of soft contact lens production for the purposes vision correction. More particularly, methods are described for creating a lens capable of dynamically altering the optical power of a soft contact lens, while in the eye, through gaze dependent use of fluid dynamics. The lens thus created may be used for the correction of emmetropia with presbyopia, simple myopia with presbyopia, compound myopic astigmatism with presbyopia, simple hyperopia with presbyopia and compound hyperopic astigmatism with presbyopia or medical conditions like post operative aphakia or pseudophakia, or even accommodative and convergence dysfunctions like accommodative infacility or convergence excess.
2. Description of the Prior Art
Some forty years ago, contact lenses (or contacts) started to be used as a common alternative to glasses to address both distance and near blurred vision. The two types of contact lenses that are presently in use are either PMMA/Rigid Gas Permeable or Hydrophilic Soft contact lenses, with the soft contact design dominating the majority of the retail market by a large margin.
Originally the lenses were produced to remedy only blurred distance vision from either near sighted or far sighted prescriptions. As the field matured more sophisticated designs become available to correct astigmatism (a football shaped eye) in addition to near and far sightedness.
As the age of contact lens wearing population aged the additional need for correcting near vision blur came into play. Generally the way in which contacts have achieved correcting both distance and near vision is either through a translating design or through what is called simultaneous vision designs.
Translating hard contact lenses designs work by having at least two separate optical zones (a bi-focal) in the lens and take advantage of the fact that they move around on the cornea. These lenses are fit such that the lower edge of the contact rests against the lower lid so that as the wearer looks from a distant object, downward to a near object, the lens stays stationary at the lower lid as the eye rotates downward behind the lens so as to be looking through the near vision portion of the contact. This effectively causes the lens to “translate” on the eye.
Simultaneous designs for both hard and soft contacts were developed to address how to focus on distance and near objects when a contact lens is fit to remain essentially in the same location with respect to the optical axis of the eye even during the blink. These lenses currently addressed this issue by creating multiple refractive surfaces disposed directly along the visual axis. Examples of designs used for this purpose include aspheric, diffractive, concentric power rings, and refractive islands. Unfortunately all of these designs focus light coming from different distances onto the retina simultaneously. This is why they are called simultaneous vision designs. As one could imagine these designs result in double or multiple exposures on the retina, which significantly degrade the quality of the retinal image. This is a classic example of attempting to engineer a static solution to a dynamic problem. In other words, the best solution is to create a contact lens, which would mimic the ability of the human eye to dynamically change its focus to whatever it is attending to.